Side-by-side mattress testing · 144+ comparisons published
Updated May 2026
Category
Serta iSeries NXG 3500 Medium Foam
Personal Comfort A8 Number Bed
Comfort
Not lab tested
Not lab tested
Support
Not lab tested
Not lab tested
Cooling
Not lab tested
Not lab tested
Edge Support
Not lab tested
Not lab tested
Motion Isolation
Not lab tested
Not lab tested
Durability
Not lab tested
Not lab tested
Value
8/10
8.7/10
Blank cells mean that model has not completed our instrumented lab protocol, so we publish no measured score for it. We never estimate a number we have not recorded.
Quick Specs Comparison
Spec
Serta iSeries NXG 3500 Medium Foam
Personal Comfort A8 Number Bed
Price (Queen)
$2,599
$2,799
Type
Memory Foam
Air Chamber Number Bed
Firmness
5.5/10
5.5/10
Height
Varies by comfort level
13 inches
Trial
120 nights
120 nights
Warranty
10 years
25 years (limited)
Shipping
Free shipping
Free shipping in the continental US
Key Advantages
Why Choose Serta iSeries NXG 3500 Medium Foam
- Deep memory-foam contouring with a medium feel
- Ultimate Edge support is unusually firm for an all-foam bed
- CoolFeel Plus counters the usual memory-foam heat
Why Choose Personal Comfort A8 Number Bed
- 45 firmness settings per side, finer than Sleep Number's scale
- 25-year limited warranty with individually replaceable components
- Typically $800–$1,200 less than a comparably equipped Sleep Number i8